Answer:
They must make lunches of a number greater than 8 to make a profit.
Explanation:
Let there be x lunches the student has to make.
So, the selling price of the x lunches will be 4x.
Now, they had to pay an advertising fee of $20 and the ingredients cost $1.5 to make each lunch.
So, the total making charges of x lunches is (20 + 1.5x).
To make a profit the condition is 4x > 20 + 1.5x
⇒ 2.5x > 20
⇒ x > 8.
Therefore, they must make lunches of a number greater than 8 to make a profit. (Answer)